US4676869A
Expired / Lapsed
US
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Integrated circuits having stepped dielectric regions
Assignee: Nokia Bell Labs
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Filing: 1986-09-04
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Granted: 1987-06-30
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Expires: 2006-09-04
Abstract
Abstract Deposited silicon dioxide may be used as a field oxide layer or for other dielectric purposes in integrated circuits. However, etching a pattern in the layer usually produces steep sidewalls that prevent good step coverage of subsequently deposited conductor layers. The present technique forms the dielectric in at least two layers having different densities. A sequence of anisotropic and isotropic etching results in stepped sidewalls, providing good linewidth control and good step coverage of subsequently deposited material.
Inventors
- 👤 Kuo-Hua Lee
- 👤 Samuel E. Polanco
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 10:58
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/20; H10P50/28; H10P50/282; H10P50/283; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/014; H10W10/0145; H10W10/10; H10W10/17; H10W20/00; H10W20/01; H10W20/071; H10W20/081
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
117 words
A method of making a solid state device Characterized by steps comprising: forming a first dielectric layer having a given density on a surface of a semiconductor device precursor; forming a second dielectric layer having a density less than said given density on said first layer; depositing a resist layer and lithographically defining a pattern in the resist; anisotropically etching said pattern through said second dielectric layer and into said first dielectric layer; removing said resist layer; and exposing the first and second dielectric layers to an isotropic etchant so that said second layer etches at a faster rate than said first layer, whereby a recessed edge of said second layer on said first layer is achieved.
Claim 2
Independent Claim
117 words
A method of making a solid state device Characterized by steps comprising: forming a first dielectric layer having a given density on a surface of a semiconductor device precursor; forming a second dielectric layer having a density less than said given density on said first layer; depositing a resist layer and lithographically defining a pattern in the resist; anisotropically etching said pattern through said second dielectric layer and into said first dielectric layer; removing said resist layer; and exposing the first and second dielectric layers to an isotropic etchant so that said second layer etches at a faster rate than said first layer, whereby a recessed edge of said second layer on said first layer is achieved.
Claim 3
Dependent Claim
48 words
The method of claim 1 wherein said step of anistotropically etching is terminated prior to etching completely through said first layer, thereby retaining a portion of said first layer at the bottom of the etched region, and wherein said step of isotropically etching removes the portion retained thereby.
Claim 4
Dependent Claim
25 words
The method of claim 1 wherein the thickness of said second layer as formed is greater than the thickness of said first layer as formed.
Claim 5
Dependent Claim
32 words
The method of claim 3 wherein the step of exposing said layers to an isotropic etchant reduces the thickness of said second layer to less than the thickness of said first layer.
Claim 6
Dependent Claim
14 words
The method of claim 1 wherein said first and second layers are silicon dioxide.
Claim 7
Dependent Claim
19 words
The method of claim 5 wherein said first layer is formed by deposition of silicon dioxide on said surface.
Claim 8
Dependent Claim
35 words
The method of claim 6 wherein said first layer is densified by heating to an elevated temperature so that its height is reduced at least one percent prior to said forming said second layer thereon.
Claim 9
Dependent Claim
23 words
The method of claim 1 wherein said surface comprises silicon, and said first layer comprises silicon dioxide that is grown on said surface.
Claim 10
Dependent Claim
15 words
The method of claim 1 wherein said anisotropically etching is accomplished by reactive ion etching.
Claim 11
Dependent Claim
22 words
The method of claim 1 wherein at least said second layer is silicon dioxide, and said isotropic etchant essentially comprises hydrogen fluoride.
Claim 12
Dependent Claim
19 words
The method of claim 1 wherein said dielectric layers comprise a field oxide isolation region of an integrated circuit.
Claim 13
Dependent Claim
23 words
The method of claim 1 wherein said first dielectric layer comprises a grown silicon dioxide layer and a densified deposited silicon dioxide layer.
Claim 14
Dependent Claim
23 words
The method of claim 1 further comprising the step of depositing a layer of conductive material on at least said second dielectric layer.
Claim 15
Dependent Claim
12 words
The method of claim 13 wherein said conductive material is doped polysilicon.
Claim 16
Dependent Claim
12 words
The method of claim 13 wherein said conductive material is a metal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-06-29 | 1990-12-29 | 1991-06-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-29 | 1994-12-29 | 1995-06-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-29 | 1998-12-29 | 1999-06-30 | $7700.00 | Window Closed / Lapsed |